TWI469234B - Electronic device with wire bonds adhered between integrated circuits dies and printed circuit boards - Google Patents

Description

Electronic device having a wire connection attached between an integrated circuit die and a printed circuit board

The present invention relates to the field of integrated circuits. In particular, the present invention relates to the wiring between the circuit board on the integrated circuit die and the contact pads.

Integral circuits fabricated on germanium wafers are often referred to as "grains." For the purposes of the specification, the term dies is used for reference lithography, which is fabricated on a wafer substrate by conventional etching and deposition techniques commonly used in semiconductor fabrication. The integrated circuit (IC) is connected to the printed circuit board by wire connection. The wire is a very thin metal wire - about 25 to 40 microns in diameter - since most contact pads extend along one side of the wafer substrate to most contacts on a printed circuit board (PCB). Wire-bonding is an electrical interconnection technique that is widely used due to the speed and accuracy of modern wire-bonding machines commonly referred to as wire connectors.

The wire connector is an automatic device that fuses a small length of metal wire from the contact wires of the integrated circuit die from a plurality of conductors on the PCB. The wire is fed through a bonding tool that uses some combination of pressure, heat, and/or ultrasonic waves to attach the wire to the bond pad via a solid phase fusion process. The two most common types of connectors are known as wedge bonding and ball bonding. By means of the two types of connectors, the individual wires are connected to the conductors on the PCB by the bonding pads on the integrated circuit (IC) die. This is because the metal wire from the majority of the contact pads to the PCB is made longer to accommodate the change in the gap between the PCB and the majority of the bonding pads due to thermal expansion, flexibility of the components, and the like.

To protect and strengthen the wire bonds, they are sealed into epoxy beads called encapsulants. The top of the metal line curvature is often about 300 microns higher than most contact pads, although some wire connections can even extend even higher. As the name suggests, the encapsulant must encapsulate the full length of the metal lines such that the encapsulant beads extend to protrude above about 500 microns to 600 microns above most contact pads.

If the die is simply an electronic microprocessor, it is less necessary to maintain tight control of the encapsulant bead size. However, if the die has a microelectromechanical system (MEMS) with an active upper surface, it may be necessary or desirable to have the active surface of the die close to the other surface. This condition applies to inkjet printheads. Printing media close to the nozzle array can affect print quality. Likewise, if the cleaning surface passes over the nozzle, the encapsulant beads may interfere with the sweep contact.

Other problems arise because the sides of the encapsulant beads are not straight. One technique commonly used to deposit encapsulant involves direct extrusion from a needle to a wire array. The amount and location of the encapsulant on the die is less precise. A slight variation in pump pressure or needle speed causes the bead side that contacts the active surface to bend reasonably. When the bead side is not straight, it must be sufficiently separated from the active parts on the active surface to adequately accommodate the perturbation. Separating the electrical contacts from the active portions on the active surface (eg, inkjet nozzles) can be used for useful wafer real estate and reduce the number of dies that can be made from wafer discs.

In view of the widespread use of ink jet print heads, the invention will be described with particular reference to its application in the art. However, it is generally understood by the worker that this invention is also applicable to other integrated circuits or other support structures bonded to the PCB.

According to a first aspect, the present invention provides a method of forming a series of wires connected between a row of contact pads on a die, and a set of corresponding conductors on the support structure, the method comprising the steps of: bonding the wires with individual wires Each of the plurality of contact pads on the granule is electrically connected to a corresponding conductor on the support structure, each of the plurality of wires extending from the contact pad to the conductor in a curved shape; and each of the plurality of wires is individually pushed The arc is collapsed and the wire is plastically deformed so that the wire joint maintains a flatter shape under plastic deformation.

The strength of the wire connection is known to be small; it is a 3 to 5 gram force level. However, Applicant's work has found that the wire joint structure is sufficiently strong to withstand some degree of work hardening that occurs due to plastic deformation. The curved arc of the wire can be deformed to form a flat profile without yielding on the electrical connection to the PCB. The Applicant's above reference USSR 11/860,539 (our file MPN008US) discloses a technique for simultaneously pushing some or all of the wire loops of the wire array. This so-called gang wire pushing technique is effective, but further developments have shown that individual wire joints are more individually controlled and more easily implemented in a large number of processes.

Preferably, adjacent wires in the wire series are sequentially pushed. In still another preferred embodiment, the step of forming the wire array uses a wire splicer for moving between the plurality of contact pads and their respective corresponding conductors, and sequentially pushing the wire bonding structure on the wire splicer Lines are connected. Preferably, the wire engaging structure and the bonding tool are configured to move synchronously. Preferably, the wire engaging structure pushes the wire connection in close proximity to the wire formed by the joining tool. Preferably, the wire connector is a wedge type wire connector, and the tooling tool is wedged, and has a wire clamp at the distal end, so that during use, the wire clamp holds a length of metal wire to make a majority contact with the die. One of the pads is in contact to form a fusion connection before moving to the corresponding conductor on the PCB and the other end of the welding wire and the formal wire is connected, and the wire bonding structure has a push wire surface contacting the wire, the push wire surface abutting On the clamp, and relative to the movement of the wedge, toward the IC die, 1.0mm (mm) to 1.6mm behind the clamp. In the special form, the push surface is closer to the PCB and the clip, and the distance is between 50 microns and 400 microns. In some embodiments, the wire array does not extend more than 150 microns above the majority of the contact pads of the IC die. In the preferred embodiment, the wire array does not extend more than 50 microns above the majority of the contact pads of the IC die. In a preferred embodiment, the wire is attached to a plurality of contact pads with a wire bond strength greater than 3 grams.

Preferably, the majority of the contact pads are separated from the corresponding conductors on the PCB by more than 1 mm. In yet another preferred embodiment, the contact pads are between 2 mm and 3 mm from the corresponding conductors on the PCB. In some embodiments, the PCB has a support structure and a flexible PCB, and the support structure must be configured such that a plurality of conductors are adjacent to a plurality of contact pads on the die. In a particular embodiment, the support structure has a die mounting region for supporting the die, the die having a back surface opposite the die mounting region and an active surface opposite the back surface, the active surface having a plurality of contact pads, and The die mounting region is raised relative to the remainder of the support structure such that the contact pads are raised relative to the conductors of the support structure. In a particularly preferred embodiment, the PCB is a flexible PCB and the support structure is a liquid crystal polymer (LCP). Preferably, the active surface has a plurality of functional elements separated from the contact pads of the die by less than 260 microns. In a particularly preferred embodiment, the die is an ink jet print head IC and the functional component is a nozzle through which ink is ejected. In certain embodiments, the support structure is a liquid crystal polymer (LCP).

Preferably, the wire is covered in a bead of encapsulant which extends less than 200 microns above the active face of the die.

Preferably, the wire is covered in a package bead having a profile surface that is parallel to and spaced apart from the active surface by less than 100 microns.

Preferably, the wire array is covered in an encapsulant bead having a flat surface and inclined relative to the active surface.

Preferably, the wire is covered in the encapsulant beads, the encapsulant beads extending less than 200 microns above the active face of the grains.

Preferably, the wire is covered in an encapsulant bead which is a thixotropic epoxy when uncured.

Preferably, the wire is covered in a bead of encapsulant which is an epoxy resin having a viscosity greater than 700 cp when uncured.

In a particular embodiment, the printhead IC is mounted in a printer that is less than 100 microns from the paper path during use.

According to a second aspect, the present invention provides a wire connector for electrically connecting integrated circuit dies, the integrated circuit die having a conductor on a printed circuit board, the wire splicer comprising: a bonding tool for The integrated circuit die attaches the wires to the majority of the conductors of the printed circuit board; and the wire bond structure is used to deform the wire bonds.

Preferably, the wire engaging structure pushes the wire to plastically deform it.

Preferably, the wire bonding structure is configured to push the wire to an adhesive surface between the integrated circuit and the majority of the conductors of the printed circuit board.

Preferably, the wire engaging structure is flexible relative to the bonding tool.

Preferably, the wire engaging structure is configured to move in synchronism with the bonding tool.

Preferably, when one of the plurality of wires is formed, the bonding tool moves from the integrated circuit to the conductor, and the wire bonding structure has a push surface, which is located behind the bonding tool with respect to the moving direction when forming a plurality of wires. 1.0mm to 1.6mm.

Preferably, the integrated circuit die is mounted on the support surface and the push surface is closer to the support surface than the bonding tool, between 50 microns and 400 microns apart. Preferably, the wire connector is a wedge type wire connector, and the tooling tool is wedged, and has a wire clamp at the distal end, so that during use, the wire clamp holds a length of metal wire to make a majority contact with the die. One of the pads is in contact to form a soldered connection prior to moving to the corresponding conductor on the PCB and soldering the other end of the wire and the official wire. Preferably, the push surface is formed of a material having a smaller hardness than the wire.

Preferably, the wire is formed from a wire segment having a wire gauge between 15 microns and 75 microns. In the special form, the wire gauge is about 25 microns.

In some embodiments, the wires are attached to individual contact pads on the IC die and are not extended over 150 microns above the majority of the contact pads of the IC die. In the preferred embodiment, the wires are not extended over 50 microns above the majority of the contact pads of the IC die.

Preferably, the majority of the contact pads are separated from the majority of the corresponding conductors on the PCB by more than 1 mm. In yet another preferred form, the majority of the contact pads are spaced between 2 mm and 3 mm from the majority of the corresponding conductors on the PCB. In some embodiments, the PCB has a support structure and a flexible PCB, and the support structure must be configured such that a plurality of conductors are adjacent to a plurality of contact pads on the die. In a particular embodiment, the support structure has a die mounting region for supporting the die, the die having a back surface opposite the die mounting region and an active surface opposite the back surface, the active surface having a plurality of contact pads, and The die mounting region is raised relative to the remainder of the support structure such that the contact pads are raised relative to the conductors. In a particularly preferred embodiment, the PCB is a flexible PCB and the support structure is a liquid crystal polymer (LCP). Preferably, the active surface has a plurality of functional elements separated from the contact pads of the die by less than 260 microns. In a particularly preferred embodiment, the die is an ink jet print head IC and the functional component is a nozzle through which ink is ejected. In certain embodiments, the support structure is a liquid crystal polymer (LCP) mold.

According to a third aspect, the present invention provides an electronic device comprising: an integrated circuit die having a plurality of contact pads; and a printed circuit board having a plurality of conductors respectively corresponding to each of the plurality of contact pads The wire is connected to each of the plurality of contact pads electrically connected to the corresponding conductor; and the adhesive face is located between the contact pad and the corresponding conductor, wherein the wire is fixed to the adhesive face.

According to a fourth aspect, the present invention provides a method of reducing the height of a wire-bonded neutral wire loop, electrically connecting an integrated circuit die having a contact pad to a printed circuit board having a conductor, the method comprising the steps of: Installing the integrated circuit die to separate the contact pad from the conductor; positioning an adhesive surface between the contact pad and the conductor of the integrated circuit die; attaching a metal wire to the contact pad Or one of the conductors; pulling the wire toward the contact pad or the other of the conductor; allowing the wire to contact the bonding surface; attaching the wire to the contact pad or another of the conductor The wire is attached to the adhesive surface and is located at a point between the ends thereof.

This aspect of the invention is intended to achieve that the wire bonds can be attached to the underlying support structure without adversely affecting the joint strength or function of the wire. Attached to most of the wires is connected to the end of the loop between the ends to provide reliable and controlled production. Since the individual metal wires cannot bounce back when the wire bonding structure is detached, the height of the wire-bonded product is smaller than that achieved by inducing plastic deformation. It should be noted that the plastic deformation of the wire also involves first elastically deforming the wire. When the push-wire structure is withdrawn, the elastic deformation is removed.

No modification can be made to the bonding tool, and the wire is attached while the wire connector is forming the joint. Applicants have discovered that wire bonding typically allows the wire to contact the surface between the die and most of the conductors on the printed circuit board when forming the bond. Once the wire is fused to the contact pads on the die, the bonding tool is pulled toward the conductor on the printed circuit board. When it is pulled through the gap between the die and the printed circuit board, the wire hangs down and rests on the bottom surface. Once the bonding tool welds the other end of the wire to the conductor, and the wire clip directly behind the bonding tool interrupts the feeder by the wire until the pulling force disappears, the residual pulling force in the circuit rebounds even if it is upward. If the metal wire is brought down to the adhesive surface when the ultrasonic wave is welded to the printed circuit board, it cannot spring back upward.

Preferably, when the wire is formed, the wire is moved by the wire to contact the adhesive surface.

Preferably, the adhesive surface is a side of the double-sided adhesive tape. Preferably, the integrated circuit die and the PCB are mounted to the support structure such that they are adjacent and separated. Preferably, the PCB is a flexible PCB and the support structure is an LCP (liquid crystal polymer) mold. Preferably, the integrated circuit die is mounted to the support structure by a die attach film and the adhesive face is provided by a portion of the die attach film.

Figure 1 shows a conventional technique for applying encapsulant beads to a plurality of wires. The die 4 is mounted on a support structure 6 adjacent to the flexible PCB 8 (flexible printed circuit board). The die 4 has a row of contact pads 10 along an edge, and the flexible PCB 8 has a corresponding bond pad 12. Wire bonds 16 extend from the majority of contact pads 10 to a plurality of bond pads 12. Power and data are transmitted to the die 4 through the conductive traces 14 in the flexible PCB 8. This is a simplified diagram of the die mounted in several electronic devices. An example of a die mounted PCB mounted on an LCP (Liquid Crystal Polymer) module is an example of such a die mounted configuration as described in USSN 11/014769 (our file RRC001US). The average worker knows that the die can also be mounted directly to the hard PCB by the stitches formed thereon.

Wire bonds 16 are covered in the beads of encapsulant 2 to protect and strengthen the bond. The encapsulant 18 is directly dispensed with the encapsulant 2 at the wire connection 16. Encapsulant beads 2 are often three individual beads - two so-called barrier encapsulants 20 and one encapsulating encapsulant 22. The barrier encapsulant 20 has a higher viscosity than the encapsulant 22 and is used to form a channel that retains the encapsulating beads. The height H of the beads 2 above the grains 4 is typically about 500-600 microns. This does not pose a problem in most electronic devices. However, if the grains have active surfaces that are subject to operation on other surfaces, the beads may become an obstruction.

Rising grain relative to flexible PCB

Figure 2 shows the step support structure 6 of the wafer mounting region 26 raised relative to the PCB mounting region 24 (or at least the mounting area of the PCB bonding pads). With the die 4 on the wafer mounting region 26, the wire 16 is lower than the active surface 28 of the die 4. In fact, the wire bond 16 attached to the contact pad 10 can be the apex of the arc (note that the wire is curved to adjust the relative movement of the die to the PCB). When the wire 16 is coated with encapsulant 2, the beads have a reduced height H that is higher than the active surface 28 of the die 4. If the beads of encapsulant 2 use two kinds of beads of the encapsulating agent 20 and the encapsulating agent 22, the position, capacity and viscosity of the beads must be considered. Beads of less than 100 microns are highly achievable, and beads of less than 50 microns are highly feasible by additional measures such as wire-line collapse and bead configuration.

The height of the wire bonds 16 is about 34 microns above the grain size when the grain 4 is raised above the flexible substrate 8 410 microns. At a grain elevation of 8 610 microns above the flexible PCB, the height of the wire is about 20 microns. Even further ridges of the grains are shown to have a further reduction in the thickness of the fresh or wireless junction at a step of 710 microns with a wire connection height of about 20 microns.

Forming encapsulant beads by forming blades

3A to 3C show that the shaped blade 30 forms the encapsulant 2. The support structure is again stepped to reduce the height of the wire 16 above the die 4. Prior to curing of the epoxy encapsulant 2, the forming blade 30 moves past the die 4 and the wire in the predetermined path. As shown in FIG. 3B, the blade 30 displaces the top of the bead to its flexible PCB side to form a flat top surface 32 that is above the substantially reduced height H of the die 4.

Encapsulant beads 2 can be a plurality of individual beads or a single bead of a material as shown in Figure 1. However, in order to tightly control the shape of the encapsulant, the encapsulant material used should have a viscous flow, that is, once the self-priming needle is deposited, or by the configuration of the blade 30, the material should not be under its own weight. Flow, but keep its shape until it solidifies. This requires the epoxy to have an uncured viscosity greater than about 700 cp. A suitable encapsulant is Dymax 9001-E-v3.1 wafer encapsulant manufactured by Dymax Corporation, which has an viscosity of about 800 cp when uncured. The blade 30 can be ceramic (glass) or metal and is preferably about 200 microns thick.

It is to be understood that the relative movement between the blade 30 and the die 4 can be precisely controlled. This allows the height H to be determined by the tolerance of the wire bonding method. The encapsulant 2 covers and protects the wire bonds 16 as long as H is higher than the nominal height of the wire bonds. With this technique, the height H can be easily reduced from 500-600 microns to less than 300 microns. If the height of the line-arc is also reduced, the height H of the encapsulant beads can be less than 100 microns. Applicants used this technique to configure the encapsulant on the printhead die to a height of 50 microns below its lowest point. As shown in Figure 3C, the lowest point in front of the encapsulant and the blade 30 form an inclined surface 32 on the top surface of the bead. The printhead repair system uses this inclined surface when cleaning paper dust and dry ink from the nozzle face. This shows that the technique not only reduces the height of the encapsulant beads, but also forms a surface that can perform a function different from the package-only bonding. The blade edge profile and blade path relative to the die can be configured for a variety of shapes to form a surface having a variety of shapes.

Plastic deformation of line arc

Figures 4A through 4C show another technique for reducing the shape of the wire. Figure 4A shows the die 4 connected to the flexible PCB 8 via a wire bond 16. Although the step support structure 6 reduces the height of the line arc compared to the flat support structure, the wire connection still has a natural tendency to bounce upward rather than downward toward the step angle. Wire bond 16 is typically about 32 microns in diameter and has a tensile force of 3 to 5 grams of force. The pulling force is a tensile load that cuts off the connection to the contact pad 10 or the bonding pad 12. If such structures are fragile (one of the reasons for coating encapsulants), it is conventional practice to avoid any contact between the curved arc and other solid surfaces.

As shown in Fig. 4B, the arc of the wire 16 can be collapsed by the pusher 34. The pusher 34 displaces the wire 16 to deform the arc sufficiently elastically and plastically. Applicants have shown that contact with the thread pusher 34 can result in local work hardening in the wire, but as long as the thrust is not excessive, it does not break. The ends of the pusher 34 are rounded to avoid stress concentration points. The pusher can be a tip for engaging a single wire or blade that simultaneously pushes over a plurality of wires.

Referring now to Figure 4C, the pusher 34 is withdrawn and the wire is springed back toward its original shape to relieve elastic deformation. However, it is still plastically deformed and greatly reduced in line height higher than that of the crystal grains 4. Tests have shown that the initial line loop height of about 200 microns can be reduced to about 35 microns using this technique. The test also showed that the tensile strength of the plastically deformed metal wire was maintained at about 3 to 5 grams of strength.

The shape of the wire is not controlled, and the wire is more or less deformed at will. However, pushing the wire to bring it closer to the die provides a more uniform collapse line. Applicants' work has shown that bonding metal wires of about 200 to 300 microns provides the best results in the grains.

As shown in FIG. 4D, the die 4 and the flexible PCB 8 are mounted to the flat support structure 6. As discussed above, this means that the original loop height of the wire arc is much higher than the die 4 by about 400 microns. Therefore, when the loop is collapsed by the pusher, the metal wire has more plastic deformation. Even so, the applicant's results show that the residual loop height after the push line is about 20-50 microns.

Figures 5A and 5B show a collapse line 16 overlaid with encapsulant beads 2. Even if the beads are not configured prior to curing, the height H of the beads above the grains is still much smaller than the beads required to encapsulate the original undeformed metal line loop.

Coating agent by forming blade

Figures 6A, 6B and 6C show the use of shaped vanes 30 in place of the encapsulant beads of the spitting needle (see Figures 1 and 2). As mentioned above, the flow rate of the encapsulant from the ejection needle may vary, which results in a large positional change of the encapsulant in front of the active surface of the die 4. Therefore, any functional component on the active surface of the die must be sufficiently spaced apart from the contact pad 10 to allow for the front of the encapsulant to spread.

The encapsulating agent is applied by the forming blade to avoid the problem caused by the flow velocity variation of the ejection needle. As shown in Fig. 6A, the beads of the encapsulant 40 can be formed on the shaped blade 30 by simply dropping it into an uncured encapsulant epoxy storage tank. Of course, the beads 40 can also be formed by any other convenient means, such as operating a spit needle along one end of the blade 30.

Figure 6B shows the blade 30 which has been lowered to cause the bead 40 to touch the die 4. When the encapsulant material contacts the surface of the die, it wets and penetrates along the surface while remaining against the edge of the blade. The blade 30 is maintained at a predetermined height above the die 4 and moved across the bead 2 to flatten and reduce its shape. The encapsulant displaced by the blade 30 from the top of the bead 2 diffuses across the PCB side of the bead 2. Whether the expansion of the package exceeds the need for further diffusion across the PCB is fine. As long as the wire bonds 16 and the bond pads 12 are covered, there is no disadvantage to any additional encapsulant on the surface of the PCB 8.

In Fig. 6C, according to the above technique, the height of the wire bonding 16 is reduced by causing the arc to collapse. As explained above, the beads 2 deposited by the ejection needle need not be so large that the wire bonds 16 are covered once collapsed. Moreover, the vanes 30 can be closer to the die 4 than the wire bonds 16 when the encapsulant 16 is formed. Therefore, the bead shape in Fig. 6C is substantially lower than that in Fig. 6B.

Control of the front of the encapsulant

When the encapsulant material is dispensed from the ejector needle, small changes in flow rate may cause the beads to bulge at higher liquid flow points. As a result, the side of the bead that is in contact with the active surface of the die is not straight and has a significant perturbation. These perturbations must be adapted between the majority of the contact pads and any functional components on the active surface. The spacing between the majority of the contact pads and the functional components depletes useful wafer space. Applicants have previously developed a 260 micron array of die grains between the contact pads and the first row of nozzles. Better control of the front of the encapsulant reduces the space between the majority of the contacts and the majority of the operating elements and thus reduces the overall size. Therefore, the design is smaller and more sheets are made from the original wafer.

As shown in Figures 7A and 7B, the shaped blade 30 is used to control the encapsulant bead front face 36. The blade 30 is positioned above the die 4 to form a gap 42 between its lower edge and the active surface 28. When the ejection needle 18 is dispensed with the encapsulant material 44, it flows to the active surface, one side of the blade, and the material droplets extend through the gap 42. Due to the flow limitation created by the gap, the flow change has a reduced effect on the droplet size flowing through the gap. Thus, the front face 36 of the encapsulant is in close contact with the lower edge of the blade 30.

As shown in Figure 7B, once the self-priming needle is dispensed, the contoured blade 30 is in place to configure the encapsulant beads. The blade 30 simply moves over the die 4 in a direction away from the nozzle 38. This maintains the front face 36 of the encapsulant and flattens out of the encapsulant beads 2 above the wire bonds 16.

By wire connector to make the line die

Figures 8 and 9 show techniques for individually deforming each of the wire arcs using a wire connector. This has the advantage over the techniques shown in Figures 4A through 4C of the above "plastic deformation of the line arc" section. First, the wire joint deformation is more time-saving than the push line alignment when the wire-bonding wire is attached as a separate production step. Second, it has been found that individual bonding and deformation of each of the wire strands provides a uniform result in wire deformation and joint strength.

Figure 8 is a schematic perspective view of a wire bonder 46 forming a plurality of contact pads 10 and a plurality of conductors 12 on the flexible PCB 8 with individual wires. The print head IC 4 is attached to one side of the die attach film 58 as shown. Next, the die attach film 58 is attached to the LCP die 6. The laser sputter holes feed ink through the die attach film 58 to the nozzle array 38. The LCP die 6 has a stepped surface 60 that causes the printhead IC 4 to swell relative to the flexible PCB 8. As described above, this helps to reduce the height of the wire harness 16.

Wire connector 46 is commonly referred to in the industry as a "wedge type" wire connector. The wedge 48 receives the storage of the feed line 56 at its distal end. One of the plurality of contact pads 10 is fused to the print head IC 4 using a combination of pressure, heat and ultrasonic energy. Figure 8 contains an enlarged insertion between the display wire 16 and the conductor 12. The end of the wire has a flattened section 54 formed by the tip of the wedge 48. Adjacent to the flat section 54 is a neck 52 in which the wire 16 is moved to its circular cross section. The neck of the wire is work hardened and is particularly susceptible to plastic deformation. In view of the greater tendency at the neck 52, the wire connector 46 incorporating the wire engaging structure 50 is pushed over the wire 16 of the region. However, the wire bond structure 50 that does not contact the wire bond 16 that is too close to the neck 52 can interrupt the wire. Skilled workers know that work hardening increases the embrittlement of metals. Applicant's tests have found that the alignment wire engages the structure 50 such that its tip is between 1.0 mm and 1.6 mm behind the wedge tip (relative to its movement from the die to the flexible PCB) and 50 microns to 600 below the wedge tip. Micron produces the appropriate results. In particular, the tip of the wire-engaging structure 50 is between 1.2 mm and 1.5 mm behind the wedge tip and 100 microns to 300 microns below the tip of the wedge for best results. This configuration causes the wire bonds 16 to be less than 50 microns above the nozzle array 38, each having a bond strength between 3.5 g and 5 g.

The wire bonding structure 50 is formed of a material having a surface hardness smaller than that of the metal wire. This avoids surface depression of the metal lines, which may later become a stress concentration area.

Adhesive line to reduce loop height

Figure 10 is a schematic cross-sectional view of another technique for reducing the height of the wire loop. The adhesive face 62 is located on the LCP die 6 between the majority of the contact pads 10 of the printhead IC 4 and the corresponding conductors 12 on the flexible PCB 8. Applicants have discovered that the wire connector typically allows the wire tab 16 to hang down and contact the surface between the die and the PCB when the wire is bonded to the PCB conductor. Once the wire is fused to the contact pads on the die, the bonding tool pulls it toward the majority of the conductors on the printed circuit board. When it is pulled through the gap between the die and the printed circuit board, the wire hangs down and rests on the bottom surface. Once the bonding tool welds the other end of the wire to the conductor, and the wire clip directly behind the bonding tool interrupts the feeder by the wire until the pulling force disappears, the residual pulling force in the circuit rebounds even if it is upward. By positioning the bonding surface 62 at the point of contact between the metal line and the LCP 6, the wire connection 16 cannot be bounced back up to the same height.

The bonding surface 62 can be a double-sided adhesive tape that is sprayed onto the LCP 6 when the die 4 and the flexible PCB 8 are fixed, or which can simply be an extension of the die attach film 58.

This document is merely illustrative of the invention. The general person can immediately think of a number of changes and modifications to the spirit and scope of the broad concept of invention.

2. . . Encapsulant

4. . . Grain

6. . . Support structure (LCP mode)

8. . . Flexible PCB

10. . . Contact pad

12. . . Bonding pad

14. . . Conductive trace

16. . . Wire connection

18. . . Spitting needle

20. . . Anti-blocking agent

twenty two. . . Filling encapsulant

twenty four. . . PCB mounting area

26. . . Wafer mounting area

28. . . Active surface

30. . . Formed blade

32. . . Flat top surface (inclined surface)

34. . . Pusher

36. . . Encapsulant front

38. . . Nozzle array

40. . . Encapsulant

42. . . gap

46. . . Wire connector

48. . . wedge

50. . . Wire joint structure

52. . . neck

54. . . Flat section

56. . . Feeder

58. . . Grain attachment film

60. . . Step surface

62. . . Adhesive surface

The embodiments of the present invention are merely exemplified with reference to the accompanying drawings, in which:

Figure 1 is a schematic view of a conventional technique for applying encapsulant beads to a plurality of wires;

Figure 2 is a schematic view of the die mounted to the support structure with the die mounting area raised relative to the flexible PCB mounting area;

3A, 3B, and 3C are schematic views showing the use of a movable blade to form an encapsulant bead of a desired shape;

4A to 4D are schematic views of a line connection by a plastic deformation configuration;

Figures 5A and 5B show the height reduction of the encapsulant beads used to plastically deform the wire;

Figures 6A to 6C show encapsulant beads coated to the wire using a configuration blade;

Figures 7A and 7B show the configuration of the vanes used to control the front of the encapsulant beads on the surface of the die;

Figure 8 shows the pusher installed on the connector;

Figure 9 is a schematic view of the pusher and the wire connector;

Figure 10 shows the LCP mode between the die and the flexible PCB.

4. . . Grain

6. . . Support structure (LCP mode)

8. . . Flexible PCB

10. . . Contact pad

12. . . Bonding pad

16. . . Wire connection

58. . . Grain attachment film

62. . . Adhesive surface

Claims (17)

An electronic device comprising: an integrated circuit die having a plurality of contact pads; a printed circuit board having a plurality of conductors respectively corresponding to each of the contact pads; a wire connection, the contacting Each of the pads is electrically connected to the corresponding conductors; and an adhesive surface is located between the contact pads and the corresponding conductors, wherein the wire contacts are fixed to the adhesive faces. The electronic device of claim 1, wherein the adhesive surface is a double-sided adhesive tape. The electronic device of claim 1, wherein the integrated circuit die and the PCB are mounted to the support structure such that the two are adjacent and separated. The electronic device of claim 3, wherein the PCB is a flexible PCB and the support structure is a liquid crystal polymer (LCP) mold. The electronic device of claim 1, wherein the integrated circuit die is mounted to the support structure by a die attach film, and the adhesive face is provided by a portion of the die attach film. The electronic device of claim 1, wherein the wires are formed by a plurality of metal wires of a wire gauge of 15 micrometers and 75 micrometers. The electronic device of claim 6, wherein the wire gauge is about 25 microns. An electronic device as claimed in claim 6 wherein the lines The contacts are attached to respective contact pads on the IC die, and the wires do not extend over 150 microns above the contact pads of the IC die. The electronic device of claim 8, wherein the line of the wires does not extend beyond the contact pads of the IC die by 50 microns. The electronic device of claim 1, wherein the contact pads are separated from the corresponding conductor by more than 1 mm (mm) on the PCB. The electronic device of claim 10, wherein the contact pads are between the electrodes and the corresponding conductors between 2 mm and 3 mm. The electronic device of claim 1, wherein the PCB is a flexible PCB mounted to the support structure together with the die such that the conductors are adjacent to the contact pads on the die. The electronic device of claim 12, wherein the support structure has a wafer mounting region for supporting the die, the die having a back surface in contact with the wafer mounting region and an active surface facing the back surface, The active surface has the contact pads, and the wafer mounting region is raised relative to the remainder of the support structure such that the contact pads are raised relative to the conductors. The electronic device of claim 6, wherein the wires are formed using aluminum wires. The electronic device of claim 12, wherein the active surface has functional elements that are less than 260 microns apart from the contact pads of the die. The electronic device of claim 15, wherein the die is an ink jet print head IC and the functional components are nozzles through which ink is ejected. The electronic device of claim 16, wherein the printhead IC is configured to be mounted in a printer such that the nozzles are less than 100 microns from the paper path during use.